Means and method of photographically recording electrical impulses



April 24, 1934. R FEA R 1,956,167

MEANS AND METHOD OF PHOTOGRAPHICALLY RECORDING ELECTRICAL IMPULSES Filed Oct. 20, 1950 nr. 703: Mon,

Patented Apr. 24, 1934 Nl'lED STATES PATENT OFFICE MEANS AND METHOD OF PHOTOGRAPHI- CALLY RECORDING ELECTRICAL IM- PULSES Claims.

My invention relates to electrical recording apparatus and more particularly to such apparatus wherein sound or electrical impulses ma} .be photographically recorded on film or the like.

The commonly used method of today to photographically record sound on film is accomplished by utilizing a microphone to pick up the sound waves, converting them into varying electrical impulses, further by means of an amplifier reinforcing the alternating electrical current emanating from the microphone and a camera to continuously feed a film by the aperture at a constant speed, using a light source to expose said film directly in accordance with the electri- 35 cal impulses produced by the sound impinging upon the microphone.

The source of illumination commonly supplied or used, consists of either a string or ribbon oscillograph, or a cathode ray oscillograph, commonly called a glow lamp.

The electro-mechanical oscillographs are very difficult to manufacture and are hard to tune to the proper tension used in recording high frequencies and when so tuned are extremely fragile and easily damaged by any over-load from the current fiowing through the amplifier.

Said oscillographs are used to meter light, that is maintained at a given'intensity at its source, upon the film, and the amount of light allowed to fall upon the film is metered in exact accordance with the current flowing through the wire or strings of the oscillograph.

When an alternating current passes through the wires of the oscillograph, said wires change position, or vibrate; this vibration is utilizedfor moving a small mirror, or to open or close an aperture through which light is projected upon the film in the recording camera.

The glow lamp commonly used for recording purposes consists of an anode and a cathode placed in a glass tube, said tube is highly evacuated and then a small amount of neon, helium, argon, or other gas is introduced until the pressure in said tube becomes from 2m/m to 15m/m.

The anode, as mentioned herein, may be coated with an electron emitting chemical compound, or it may be left plain; when said anode is subjected to electrical differences of potential, between the anode and the cathode of sufficient potential, the gas within said gas tube will break down and conduct said current between said anode and cathode.

In practice it is usual to excite the glow lamp with a direct current of a potential sufiiciently strong to break down the gas within the lamp,

and then to superimpose an oscillating or alternating current upon said direct current; said alternating current may emanate from an amplifier which has been used to reinforce electrical impulses, and the resulting photographic record being one of a varying density.

Therefore, it is an object of my invention to provide new and useful improvements in photo'- graphically recording electrical impulses used for recording sound and the circuit system thereof, necessary for the proper control of the sound recording circuit.

A further object of my invention is to provide said electrical circuit and said electrical system with mercury arc lamps, wherein the break-down voltage is reduced by the introduction of an inert gas such as neon, argon, helium gas or the like, at the pressure sufiiciently to cause the density of said gas within said tube to break down at 100 to 500 volts or greater.

Another object of my invention is to provide said electrical circuit and said electrical system with a mercury arc-lamp for the purpose of recording sound upon said film and provide means within said electrical circuit and system wherein all of the noise emanating from said arc-lamp is entirely eliminated and to provide said electrical circuit with means whereby any fluctuation of the current flow through the mercury arc is eliminated and the consequent production of audible noise or variation of light produced by such variation of current flow, is prevented.

Another feature of my invention is to provide said electrical circuit and said electrical system with suitable chokes placed in series with the mercury arc-lamp, an input circuit, to properly modulate said current flow through said lamp and also a separate electrical circuit causing said' arc-lamp to continuously oscillate at frequency above audibility; said high frequency current being in turn modulated by the electrical im"-' pulses which are to be recorded.

The above and further objects and advantages of my invention as will hereinafter more fully appear, I attain by the construction described in the specification and illustrated in its proper form on the drawing forming a part of my application.

Reference is had to the accompanying drawing, in which similar reference characters denote similar parts.

In the drawing:

Fig. 1 is a diagrammatical view showing a novel form of my invention connected with the soundon film recording apparatus.

Fig. 2 is the diagrammatical illustration of the oscillating circuit for controlling the recording tubes.

Fig. 3 is the diagrammatical illustration of the oscillating circuit in modified form.

Fig. 4 is another diagrammatical illustration in modified form of the oscillating circuit.

Fig. 5 is still another diagrammatical illustration in modified form of the oscillating circuit.

Describing my invention more in detail, my in vention comprises the sound recording apparatus generally designated by numeral 2, wherein the recording tube 4 is substantially positioned for recording impulses upon a film 6 (shown in dotted line), passing at a constant speed past a slit 8, of the aperture 10, substantially as shown.

Said recording tube 4 is connected with the recording tube modulating means and the amplifying means generally designated by numeral 12, by means of lead wires 14, also with the microphone 16 by means of lead wire 18.

In the Fig. 2 I have shown the amplifying means 12, connected to the sound recording tube 4 by means of a transformer 29, connected by means of lead wire 22, to the inductive resistance 24, having a variable condenser connected thereto; also having a lead wire 28, connected to the audion lamp 30, which is substantially connected to the inductive resistance 32, and the impedance 34, having lead wire 36 connected to the battery A leading to the audion lamp 30, and the battery 13 connected to the transformer 20, and the recording tube 4, by means of lead wire 38, wherein said incoming electric current supplied by said battery B into said audion lamp 30, will separate its potential energy within said audion lamp 30, and indirectly transmit said energy in the form of an out-going alternating electrical current to said mercury recording lamp 4, and wherein said outgoing current is in turn modulated by the electrical impulses which are to be recorded, causing said lamp 4, to continually oscillate at frequency above audibility.

In the Fig. 3 I have shown the construction of the circuit in modified form corresponding generally to Fig. 1, wherein said amplifying means 12 is connected to the circuit by means of a transformer 20, which is connected to the recording tube 4, and the inductive resistance 40, leading into condenser 42, where the head-phones 44, are positioned and leading through a switch 46, and the ammeter 48, to the impedance 50; said transformer 20, is connected with battery B by means of lead wire 52, and the inductive resistance 54, by means of lead wire 56. The inductive resistance 54 is connected to the audion lamp 58, by means of lead wire 60, which is also connected to the inductive resistance 62, leading to the condenser 64, to the battery C and having an impedance 68 positioned as shown; said audion lamp 58 is also connected to battery A by means of lead wire 70 and the battery 0 leading into lead wire 56 through a lead wire 72 substantially as shown.

The Fig. 4 shows another modified circuit arrangernent corresponding generally to Fig. 1, wherein said amplifying means 12 is connected through a transformer 20 to said circuit and by means of lead wire '74, is connected to the recording tube 4, through a condenser 76, the headphones 78 and by means of lead wire 80 to said transformer 20; said lead wire 80 is connected to a plurality of radio chokes leading to an impedance 84, and leading into power means 86, preferably of 350 to 500 volts; the lead wire 74 is also connected to the head-phones 88, and the am meter 90, having a recording switch 92, positioned therein.

Said transformer 20 is connected with an inductive resistance 94 by means of a lead wire 96, having a condenser 98, positioned therein and a variable condenser 100 positioned thereto; the lead wire 102, of said inductive resistance 94, leads into battery B and the lead wire 98 is connected with the audion lamp 104', and the inductive resistance 106 having a condenser 108 associated therewith; said audion lamp 104, leads into impedance 109 which is connected with the inductive resistance 106, and impedance 84, by means of lead wire 110, the audion lamp 104 is also connected with battery A by means of lead wire 111.

The purpose of said radio chokes 82, employed in this circuit is to insulate audible frequencies and to prevent any variations of current flow from passing through said tubes, substantially as shown.

In the Fig. 5 I have shown another form of circuit arrangement in modified form, which is associated with said amplifying means 12, and to transformer 20, leading into battery 13, also to the recording tube 4 having an inductive resistance 112, preferably of 100 turns, also the condenser 114, and the headphones 116 associated therewith. From the battery B, I have provided a lead wire 118 which is connected to the inductive resistance 120, preferably of 500 turns and leading into an audion lamp 122, which is associated with an inductive resistance 124, preferably of 500 turns and leading into impedance 126, which is connected to the battery A substantially as shown.

While I have described my invention with great particularity it will be clear that the same may be modified throughout a wide range. I accordingly do not propose to be limited to the exact details of construction and arrangement as shown and described herein, but reserve the right in practice to make any and all modifications that may fall within the scope of the appended claims.

I claim as my invention:

1. In combination in a sound on film recording apparatus, means for converting electrical impulses or currents that have been produced by sound into varying light impulses or rays for the purpose of exposing photographic film moving at a constant speed to the action of said varying light rays, said means being a gaseous discharge tube or glow lamp; and means for causing said glow lamp to emit light at a constant and unvarying amount when not modulated by said electro-sound impulses; said means consisting of a battery connected to the elements of said glow lamp, said battery having a sufiicient potential to break down the gas in said glow lamp and form a light emitting arc therein; and electrical means for causing a uniform and unvarying amount of current to flow from said battery thru said glow lamp when not modulated by electrosound impulses; said electrical means consisting of a suitable thermionic valve or audion tube connected with the necessary apparatus to cause impulses or currents that have been produced by sound into varying light impulses or rays for the purpose of exposing photographic film moving at a constant speed to the action of said varying light rays, said means being a gaseous discharge tube or glow lamp; and means for causing said glow lamp to emit light at a constant and unvarying amount when not modulated by said electro-sound impulses, said means consisting of a battery connected to the elements of said glow lamp, said battery having a sufiicient potential to break down the gas in said glow lamp and form a light emitting arc therein; and electrical means for causing a uniform and unvarying amount of current to flow from said battery thru said glow lamp when not modulated by electro-sound impulses; said electrical means consisting of a thermionic valve or audion tube, with a battery for supplying current to the filament of said tube, a coil connected to the grid of said tube, another coil with one terminal connected to the plate of said tube and arranged for inductive coupling to said grid coil so as to cause said tube to oscillate, means for tuning said plate coil to vary the frequency of the oscillation of said tube, and the other terminal of said plate coil connected to one terminal of the glow lamp to cause an alternating current to be impressed upon the direct current flowing thru said glow lamp.

3. In glow lamp recording, means for the purposes of photographically recording sound on film, a glow lamp, battery means for forcing a direct current thru said glow lamp, a transformer one of whose sides is connected in series with said lamp, and the other side of which is connected to an electro-sound amplifying source, for the purpose of modulating said direct current in accordance with the sound electrical impulses emanating from said amplifying source, a thermionic oscillator inductively coupled to a coil in series with the other lead between the direct current source and said glow lamp, and means for varying the intensity of the alternating current impressed upon the direct current component flowing thru said glow lamp.

4. In glow lamp recording, means for the purpose of photographically recording sound on film, a glow lamp, battery means for forcing a direct current thru said glow lamp, a transformer one of whose sides is connected in series with said lamp and the other side of which is connected to an electro-sound amplifying source for the purpose of modulating said direct current in accordance with the sound electrical impulses emanating from said amplifying source, a thermionic oscillator inductively coupled to a coil in series with the other lead between the direct current source and said glow lamp, means for varying the intensity of the alternating current impressed upon the direct current component flowing thru said glow lamp, and means for varying the frequency of the alternating current generated by said thermionic oscillator.

5. In combination in glow lamp recording, means for the purpose of photographically recording sound on film, a glow lamp, meansfor forcing a direct current thru said glow lamp, a transformer the primary of which is directly coupled to the output of an audio frequency thermionic amplifier and the secondary of which is directly and capacitively coupled in parallel with said glow lamp, means for impressing an alternating current upon said direct current component, means for varying the frequency of said alternating current, means for varying the potential of said alternating current, and choke means of high impedance for forcing said alternating current to flow thru said glow lamp and preventing uncontrolled direct current variations in said glow lamp circuit, the entire purpose of said combination of elements being to force said glow lamp to glow at a uniform and unvarying brilliancy when not modulated by an electro-sound impulse impressed upon said glow lamp circuit.

RALPH GORDON FEAR. 

